Circuit arrangement for controlling the operation of key-controlled telephone selection apparatus



July 22, 1958 K. FISCHER' 2,844,660

CIRCUIT ARRANGEMENT FOR CONTROLLING THE OPERATION OF KEY-CONTROLLED TELEPHONE SELECTION APPARATUS Filed Feb. 4, 1955 2 Sheets-Sheet 1 2 Sheets-Sheet 2 K. FISCHER CIRCUIT ARRANGEMENT FOR CONTROLLING THE OPERATION OF KEY-CONTROLLED TELEPHONE SELECTION APPARATUS July 22, 1958 Filed Feb. 4, 1955 2,844,660 ClRCUlT AGEMENT FOR CONTROLLING THE OPERATTGN t3 KEY-CONTROLLED TELEPHONE SELECTKUN APPARATUS Kurt Fischer, Munich, Germany, assignor to Siemens &

Halske Aktiengesellschaft, Munich, Germany, a corporation of Germany Application February 4, 1955, Serial No. 486,229 Claims priority, application Germany February 26, 1954 15 Claims. (Cl. 17990) This invention is concerned with a circuit arrangement for governing the operations of key-controlled signaling apparatus, especially telephone switching apparatus comprising key-operated number transmitters and automatic selectors.

The term key-operated number transmitter designates a device provided with a plurality of selection keys, for example, ten selection keys, arranged in a decade selection system, each key representing predetermined selection impulse series. By means of these keys, the digits of a called number may be dispatched at any practically desired speed; the corresponding selection impulse series are during and after the keying automatically transmitted by the device in the rhythm and with the time spacing required by the system served.

The term automatic selector designates a device which is likewise provided with a plurality of selection keys each, however, designating a predetermined subscribers number, that is, each key designating a plurality of predetermined selection impulse series. After the corresponding key has been depressed, the automatic selector carries out the selection of a subscribers number automatically.

Installations of the kind to be here considered are as is known, provided wtih storage means serving to temporarily record the mechanical or electrical criteria which are released by the actuation of the selection keys and mark the selection impulse series to be transmitted. The storage means may, for example, be relays which by their energized condition or rather to say by their actuated contacts mark the impulse series to be transmitted, or they may be capacitors which provide for such marking by their charge or their charge potential.

The invention proposes the use of magnetic storage means for the system indicated before. The circuit arrangement according to the invention comprises saturable core chokes forming storagemeans for marking current or voltage surges of selection impulse series released by the actuation of selection keys.

The characteristic marking current or voltage surges or impulses are generated by a saturable core repeater to be selectively connected with the satuable core chokes, causing a certain alteration in the magnetic induction of the choke loaded for storage, which marks the desired selection impulse series. The chokes loaded for storage are by means of a further saturable core repeater which is selectively connected therewith, brought step-by-step to a certain value of their magnetic induction, such values signifying the termination of the storing operation; the number of steps required therefor, which is determined by the value of the magnetic induction at the start of the storing, being in a fixed relationship to the selection impulse series signified by such value. The further saturable core repeater serving for the conversion of the stored current or voltage pulses into the selection impulse series corresponding thereto is for this purpose made dependent on an impulse transmitting relay.

The invention will now be explained with reference to the accompanying diagrammatic drawings, wherein:

Pig. 1 illustrates in schematic manner an embodiment of a key controlled number transmitter, the circuit deg, 2,844,660 Patented July 22, 1958 tails being shown only to the extent required for an understanding of the invention; and

Figs. 2a, 2b, 2c and 2d represent various characteristics of the switching elements used, to aid in the explanation of the electric and magnetic operations incident to the storing and the release of the stored pulses, respectively.

The key number transmitter according to Fig. 1 comprises ten selection keys T1 to T0 allotted respectively to the digits 1 to 0. Of these ten keys, only keys T1, T5, T6 and T0 are for simplification shown in the drawing. The key T1 is in part ineffective; some of its contacts being inactive. The keys T2 to T9, as shown in connection with the keys T5 and T6, are connected with tabs of the secondary winding 11 of a saturable core repeater U1. The common key contacts ltg and Ztg are closed upon actuation of each of the selection keys T1 to T0.

Let us now assume that the selection key T6 corresponding, for example, to the digit 6 is depressed. The common key contact Ztg closes a circuit for the restoring winding III of the repeater U1 and for the relay A having the contacts 3a to 6a, and over cont-act ltg a further circuit is closed for the saturable core choke for example, choke Z, by way of wiper d1 of a corresponding switch having a drive magnet D1. The repeater U1 and the choke Z1 are by direct current flowing over the contact Ztg brought to their initial magnetic condition, the magnetization in the corresponding repeaterand choke-cores assuming their respective normal saturation values responsive to the interruption of the current flow upon opening the contacts 311 and 5a.

Fig. 2a illustrates schematically the hysteresis loop of the core material for the repeater U1; Fig. 2b shows similarly the hysteresis loop of the core material of the saturable core chokes including the choke Z1. As is apparent from Fig. 2a, the magnetic induction Bul of the repeater U1 assumes after actuation of the contact 3a the residual value Ru1, and as shown in Fig. 2b, the choke Z1 (Bz) assumes after actuation of the contact 5a the residual value -Rz.

Contact 4a closes a circuit for energizing relay B having the contacts 7b to 1011. Relay B closes a holding circuit for itself, for the duration of the key depression, over its contact 812 which at the same time disconnects the relay A. Relay A releases with some delay due to the shunt of its Winding I over contact 3a. Contact 7b closes a circuit for the primary winding I of the saturable core repeater U1. The saturation of the core of this repeater is now changed by the current flowing through its winding. The magnetic induction assumes a value corresponding to the point sul in the positive saturation branch of the hysteresis loop shown in Fig. 2a. The position of the point sul is determined by the value of the current Jul which occurs upon saturation in the circuit extending over contact 7b.

The induction alteration during the change of saturation causes appearance of an induction current surge in the secondary winding II of repeated U1 which will be referred to as voltage surge or pulse, in the case of low loading of the secondary Winding, and as current surge or pulse in the case of low resistance of the secondary circuit, respectively. The voltage or current-time-integer, respectively, constitute criteria for the magnitude of this induction surge, the current-time-integer being in a known lawful relationship to the induction alternation in the primary circuit.

Fig. 2c shows in schematic manner, as a rectangular area I in the voltage-time diagram, the voltage-time-integer corresponding to the magnitude of the induction surge. In this figure U signifies the voltage appearing at the secondary winding II; t designates the time for changing magnetization. The magnitude of the integer depends solely upon the induction alteration in the primary windmg.

As shown in Fig. 2a, this magnitude may be made practically independent of the current flowing after changing magnetization or rather to say of the voltage in the primary winding, by using a core material with a sharp .saturation angle in which the saturation branches of the hysteresis loop extend substantially in parallel to the axis of the abscissa. Such core materials are known and commonly used for saturation repeaters. The magnitude of the voltage integer appearing in the secondary circuit can therefore be made largely independent of voltage fluctuations in the primary circuit.

The full induction surge over the secondary winding II which is provided with tabs connected with the keys T2 to T9 is obtained, as indicated in Fig. 2c, over the selection key T0, the keys T2 to T9 furnishing only fractional values of such induction surge. The induction surge keyed overone of the selection keys causes an alteration of the magnetic induction in the respectively connected saturable core chokes. The repeater U1 and the chokes are mutually tuned, for example, in such a manner that the magnetic induction of the core material of the choke which is effective responsive to actuation of the key T assumes the value +Rz, as is indicated in Fig. 2b. In case the key T6 is depressed, the fractional induction surge obtained irom such key will cause the rising branch of the hysteresis loop to run, for example, up to the point s6. After decay of the induction surge, the point s'6 will be reached.

Accordingly, the induction surge released by the. depression of the key T6 is stored in the form of an alteration of the normal magnetization of the choke core from Rz to s'6. This operation is accomplished during the release interval of the relay A.

Upon release of the relay A, a circuit is closed for the drive magnet D1 of the stepping switch, over contacts 611 and 9b, and the relay V'having contacts 11v to 14v, is energized in a parallel with D1. The wiper all is stepped by one step and the next successive choke (Z2) is. accordingly connected for storing. Relay X having windings XI and XII and contacts 15x to 17x is energizedover its winding I (XI) in a circuit extending by way of contact 11v. The winding I of the switch-over relay P (winding PI) is energized over contacts 12v and 17x during the energization interval of the relay X, relay P thereupon placing its contact 18p into the mark position Z. Contact 13v closes a circuit for the secondary winding II of the saturable core repeater U2, and this repeater-is thereby brought into its initial magnetic condition in a manner analogous to that described before in connection with the repeater U1. Contact 14v closes, for example,.a line loop for the subsequent transmission of the selection impulses.

Contact 18p connects the impulse relay J adapted to operate in a self interrupter circuit and having the contacts 19j to 24 Contact 20 maintains relay V energized; the initial energizing circuit of V being interrupted at contact 9b upon release of relay B responsive to. release of the selection key that may have been depressed. Contact 22 connects the secondary winding II 0f the repeater U2 in impulsing manner by way of the winding II of the'switch-over relay P (Winding PII) with the saturable core choke that may have been connected over the wiper d2 of the switch D2, in the instant case, with the choke Z1. Contact 23 closes during such operation a circuit for the primary winding 1 of the saturable core repeater U2. Contact 24f transmits impulses, for example, in the form of interruptions of the line loop L extending over contact 14 The magnetic induction B112 (Fig. 2d) of the core of the repeater U2 fluctuates responsive to the operation of contacts 22f (in its normal position) and 213i (in its actuated position) between the values corresponding to the saturation points 44142 and -su2 of thehysteresis loop shown in Fig. 2d. For example, when the relay J is in normal position, the rising branch of the hysteresis loop will run from su2 to +su2, while the descending branch will run between the identical points in the operated position of the relay. During the change of saturation, in the operated position of the relay 1, there will be induced in the winding II of the repeater a voltage or current surge which is proportional to the induction alteration, the voltage-time-integer corresponding to such surge being in Fig. 2c schematically indicated as a rectangular area II. Each such induction surge causes a proportional alteration of the magnetic induction of the saturation choke that may at the time be operatively connected, thus causing a step-by-step return to the initial value within the range of negative saturation.

In accordance with Fig. 2b, and starting with the assumption of a storage value s'6 of the magnetic induction of the choke Z1, the induction will run through the curve flight s6; 11; 22; 3-3; 4-4; 5(-Rz); 6(Rz). The points 1 to 6 of this curve flight are assumed in the operated position of the relay J and the points 1' to 4 and -Rz are assumed in the normal position of such relay.

The magnetic induction Bz is shown in Fig. 2b as depending on the current Jz flowing through the saturable core choke. Reference Jp indicates the value of the energization current of the winding II of the change-over relay P (winding PH). As will be apparent from the figure, this value is respectively first reached or exceeded in the curve portion (-Rz) -6 of the hysteresis loop responsive to the sixth energization of the relay J. Relay P thereupon energizes over its Winding II and places its armatureoontact 18p into the space position T. The circuit for relay J is thereby interrupted and the transmission of impulses ceases. Relay V and thereupon relay X restore. Their restoration intervals determine the pauses between the selection impulse series. The drive magnet D2, a switch controlling Wiper d2, is energized over contacts 18p and 15x and wiper d2 is accordingly stepped to the next saturation choke.

The switch having drive magnet D2 is provided with two contacts 25:12 and 26:12. Upon release of the relay X and during the release interval of the drive or stepping magnet D2, a circuit will be completed for the winding I of the change-over relay P (winding PI), over contacts 17:: and '25d2, wiper d2 and the saturation choke that may at that time be operatively connected, and relay P accordingly places its contact 18p again into the mark position Z, thereby again initiating the release of the next successive selection impulse series. The current flowing in the corresponding circuit is so low that the magnetic induction in the saturable core choke is substantially unafiected and its storage value is accordingly not falsified.

As described before, the switch D1 is stepped by one step incident to each storage operation responsive to each depression of a key. The switch D2 lags in its operation behind D1 as it is stepped by one step incident to each release or transmission of a stored impulse series. When the switch D2 catches up with D1 so that the wipers d1 and d2 are identically positioned, all stored selection impulse series will have been transmitted. After release of relay X and during the release interval of the drive magnet D2, a circuit will be completed for the changeover relay P, windings PI and PIII, over contacts 17x, 25d2, Wipers d2 and d1, contacts 5a, 26d2 and 16x, the

' energization of winding PIII predominating in such circuit over that of winding PI. The armature contact 18p is by such energization of Winding PIII held in its space position T and re -energization of relay I is thus prevented.

As demonstrated in the example explained in the foregoing description, the current or voltage surges induced in the winding II of the saturable core repeater U2 will cancel the induction alterations caused by the storing operations in the saturable core chokes. The arrangement may however be such that the magnetic induction of the saturable core chokes is by the effects of these induction surges altered in the same sense as during the storing, so that the value +Rz in Fig. 2b is, for example, reached after a certain number of impulses and that responsive to the next successive impulse a point is reached along the positive saturation branch of the hysteresis loop at which the change-over relay P is again energized in the indicated sense over its winding II. The connections of the selection keys T1 to T0 to the secondary winding of the repeater U1 would in such a case be interchanged.

The illustrated embodiment has however the advantage that the stray effect of the magnetic core values of the chokes is eliminated by the change of magnetization of the saturable core chokes during the storing operations. Since the magnitude of the induction surges generated by the saturable core repeater U2 can be made substantially independent of fluctuations of the operating voltage, under the previously mentioned requirements for the saturable core repeater U1, there will result a far reaching independence from extraneous influences which is not present in previously known systems.

If the digit 1 is selected by depression of the selection key T1, the magnetic induction in the saturable core choke connected for storage will not be altered because such key is not connected. The corresponding choke therefore retains the initial value -Rz as shown in Fig. 2b. Accordingly, upon transmission, the energizing current value in the winding II of the changeover relay P will be respectively reached or exceeded responsive to first energization of the relay J and such relay will be released immediately thereafter. Only one impulse will therefore be transmitted.

The value of the voltage or rather to say current-timeinteger of the effective voltage or current surges is decisive for the alteration of the magnetic induction of the saturable core chokes in the storing and in the transmission of the stored impules. Other than the above described operations may therefore be employed for the storing and the transmission of the stored impulses by the use of the saturable core repeaters or converters, for example, operations in which the product of the voltage U and the magnetization time t (Fig. 2c) satisfies the mentioned conditions. The storing therefore may be effected by the use of diiferentiated voltages the values of which are in a fixed relationship to the selection impulse series to be marked by the storing and which are connected in each case for a constant interval to the saturable core chokes; or by connecting a constant voltage during varying time intervals, in which case the durations of these time intervals are in a fixed relationship to the selection impulse series to be marked. It is also possible to efiect the storing by connecting the saturable core chokes in a capacitor charge or discharge circuit; the capacitance or the charge potential of the capacitor may thereby be varied depending on the selection impulse series to be marked. Another possibility is to magnetize the saturable core chokes over ditferent tabs of their windings, during an effective operating interval which is in any case constant, in which arrangement the different tabs or rather the corresponding number of turns are in a fixed relationship to the selection impulse series to be marked. Similar arrangements may be used for transmitting the stored marking impulse series.

Changes may be made within the scope and spirit of the appended claims.

I claim:

1. In key-controlled apparatus for effecting number selection in a telephone system or the like, a plurality of selection keys for respectively marking impulse series to be transmitted, a plurality of saturable core chokes, and means for respectively connecting said chokes with said keys for magnetically storing in said chokes the impulses respectively marked by the actuation of said keys.

2. A system and cooperation of parts as defined in claim 1, comprising a saturable core repeater cooperating with said chokes for magnetically storing therein the impulses to be transmitted.

3. A system and cooperation of parts as defined in claim 2, comprising a further saturable core repeater for converting the magnetically stored impulses to produce therefrom impulse series corresponding thereto in accordance with the series marked by said keys.

4. A system and cooperation of parts as defined in claim 3, comprising means for selectively connecting said saturable core repeaters with said saturable core chokes.

5. A system and cooperation of parts as defined in claim 3, comprising a secondary winding forming part of said first named saturable core repeater, means forming tabs connected witlrsuch secondary winding, and means for respectively connecting said tabs with said saturable core chokes to effect variable magnetization thereof.

6. A system and cooperation of parts as defined in claim 5, comprising means for selectively connecting said tabs with said saturation chokes to efiect alteration in the magnetization of a choke connected with a tab which is characteristic of a predetermined selection impulse series marked by one of said keys.

7. A system and cooperation of parts as defined in claim 6, wherein the respective normal and actuated conditions of said chokes are characterized by predetermined magnitude of magnetization thereof prevailing prior to said alteration.

8. A system and cooperation of parts as defined in claim 7, wherein the respective normal and actuated conditions of said saturable core chokes are respectively marked by a predetermined saturation thereof.

9. A system and cooperation of parts as defined in claim 7, wherein a predetermined selection impulse series is solely marked by the initial condition characterizing the magnitude of magnetization marking the initial condition of a saturable core choke.

10. A system and cooperation of parts as defined in claim 9, comprising means including said further saturable core repeater for bringing said saturable core chokes step-by-step to a magnitude of magnetization marking the termination of the transmission of the stored impulse series, the number determined by the magnitude of magnetizatiorr at the start of said transmission being in a fixed relationship to the selection impulse series marked by such magnitude.

11. A system and cooperation of parts as defined in claim 10, wherein the termination of the transmission of impulse series corresponding to magnetization of a saturable core choke is marked by reaching a magnitude corresponding substantially to the initial magnetization of such choke.

12. A system and cooperation of parts as defined in claim 10, comprising an impulse transmitting relay controlling the operation of said further saturable core repeater.

13. A system and cooperation of parts as defined in claim 4, comprising a pair of switches each having a Wiper for selectively connecting said saturable core chokes with said saturable core repeaters.

14. A system and cooperation of parts as defined in claim 13, comprising switching means operatively afiected in a circuit including said wipers for marking the termination of the transmission of all keyed selection impulse series.

15. A system and cooperation of parts as defined in claim 14, comprising an impulse transmitting relay, a pair of drive magnets for respectively operating said wipers, and means governed by said switching means for controlling said impulse relay and at least one of said drive magnets.

References Cited in the file of this patent UNITED STATES PATENTS 2,594,300 Dunlap Apr. 29, 1952 

